The present invention relates to telecommunications systems in general, and more particularly to methods and apparatus for bandwidth management for DSL modem pools.
The ever-increasing demand for high-speed data communications services and greater bandwidth is largely due to the popularity of the Internet and other data-intensive, high bandwidth applications. Both businesses and consumers are demanding higher bandwidth connections and faster Internet access. Another source for this demand is the increasing use by businesses of data communications networks (including traffic over the Internet) for the transmission of documents and electronic mail.
Digital Subscriber Loop (DSL) technology provides one approach to addressing the demand for high-speed telecommunications service. DSL technology refers to several types of services that use advanced modem elements to transmit digital signals from a data source over copper wires. Many telephone companies have embraced DSL technology as an immediate broadband solution to serve the current demand by getting more out of their existing copper infrastructure. DSL modem elements permit high data rate transmission of data over the public switched telephone network (PSTN) at multiple megabit speeds using sophisticated signal processing techniques that permit voice and data to travel simultaneously over the same analog copper twisted pair wire.
Management of co-interfering modems in a modem pool, such as where two or more modem connections are carried via the same copper wire bundle, is faced with several difficulties.
Current modem pool arrangements call for initializing one or more modems in a modem pool with a large predetermined margin, thereby diminishing throughput. Furthermore, when initializing a single modem in a modem pool, existing systems do not compensate for the co-interference of other modems that share the same bundle.
One aspect of the present invention is a system for managing overall PSD in a wire bundle by controlling the PSD of each modem element in a modem pool in such a way that the overall throughput is optimized while the overall PSD complies with PSD regulations. The present invention also provides for static and dynamic bandwidth management that maximizes the overall throughput of a transmission that is spread across a modem pool and its SNR while minimizing the overall BER.
Static bandwidth management is employed at system start-up by setting a rate for each modem in a modem pool in a way that maximizes the aggregate bit rate of the entire modem pool. The process preferably provides a consistent result for consecutive processes. Dynamic bandwidth management is employed continually at steady state to preserve the system""s SNR margin. Since DSL environments suffer from temporal effects such as external disturbances, temperature shifts, etc., it is desirable to manage bit rates after initial system start-up to minimize SNR and BER fluctuations due to such effects.
One aspect of the present invention is a method for managing the bandwidth of a modem pool having at least two co-interfering modems, the method including measuring an SNR margin for at least two of the co-interfering modems, and adjusting the bit rate of each of the co-interfering modems such that the SNR margin of each of the co-interfering modems is between a first and a second predetermined threshold.
In another aspect of the present invention the measuring step comprises measuring the SNR margin with respect to a maximum allowable BER.
In another aspect of the present invention the method further includes setting any of the modems in the modem pool to a first bit rate prior to the measuring step.
In another aspect of the present invention the measuring step is performed for each of the modems concurrently.
In another aspect of the present invention the adjusting step is performed for each of the modems concurrently.
In another aspect of the present invention the setting step is performed for each of the modems concurrently.
In another aspect of the present invention the at least two co-interfering moderns use different modulation schemes, the SNRref differs for each of said co-interfering modems, and each SNRref corresponds to one of said modulation schemes.
In another aspect of the present invention the adjusting step includes adjusting the bit rate B of a modem i according to the formula       B    l          (              n        +        1            )        =            B      t              (        n        )              +          (                        B          i                      (            n            )                          ·                              M            i                          (              n              )                                            SNR            ref                              )        +          w      t              (        n        )            
where Mi is the SNR margin of the modem i being adjusted, where SNRref is the SNR that corresponds to the maximum BER, and where wt is uniformly distributed noise over [xe2x88x92r/2, r/2] where r is a minimum bit rate increment.
In another aspect of the present invention the measuring and adjusting steps are performed a plurality of iterations.
In another aspect of the present invention the measuring and adjusting steps are performed a plurality of iterations until the SNR margin of all of the modems have been optimized such that the overall bit rate no longer improves with each iteration.
In another aspect of the present invention the measuring and adjusting steps are performed a predetermined number of iterations.
Another aspect of the present invention is apparatus for managing the bandwidth of a modem pool having at least two co-interfering modems including means for measuring an SNR margin for at least two of the co-interfering modems, and means for adjusting the bit rate of each of the co-interfering modems such that SNR margin of each of the co-interfering modems is between a first and a second predetermined threshold.
In another aspect of the present invention the means for measuring measures the SNR margin with respect to a maximum allowable BER.
In another aspect of the present invention the apparatus firer includes means for setting any of the modems in the modern pool to a first bit rate prior to the measuring step.
In another aspect of the present invention the means for adjusting is operative to adjust each of the modems concurrently.
In another aspect of the present invention the means for setting is operative to set each of the modems concurrently.
In another aspect of the present invention the means for adjusting is operative to adjust the bit rate B of a modem i according to the formula       B    t          (              n        +        1            )        =            B      t              (        n        )              +          (                        B          t                      (            n            )                          ·                              M            t                          (              n              )                                            SNR            ref                              )        +          w      i              (        n        )            
the Mi is the SNR margin of the modem i being adjusted, SNRref is the SNR that corresponds to the maximum BER, and wi is uniformly distributed noise over [xe2x88x92r/2, r/2] where r is a minimum bit rate increment.
In another aspect of the present invention the at least two co-interfering modems use different modulation schemes, the SNRref differs for each of the co-interfering modems, and the each SNRref corresponds to one of the modulation schemes.
In another aspect of the present invention the means for measuring and adjusting are operative to measure and adjust a plurality of iterations.
In another aspect of the present invention the means for measuring and adjusting are operative to measure and adjust a plurality of iterations until the SNR margin of all of the modems have been optimized such that the overall bit rate no longer improves with each iteration.
In another aspect of the present invention the means for measuring and adjusting are operative to measure and adjust a predetermined number of iterations.
In another aspect of the present invention the first and second thresholds vary for at least two of the co-interfering modems.
In another aspect of the present invention a minimum and a maximum bit rate vary for at least two of the co-interfering modems.